Among biphenyl derivatives having an inhibiting activity for aldose reductase, there have been known aldostatin (as disclosed in Japanese patent application Kokai No. 205095/1987) and FR 900280 (as disclosed in Japanese patent application Kokai No. 72144/1990), which are now under examination for their application to the prevention of therapy of diabetic complications, such as cataracts, retinal disease, neuropathy, nephropathy and so on.
Nevertheless, there is still a need to develop substances having a higher aldose reductase inhibiting activity than those of the prior art.
The inventors have studied the pharmacodynamics of various compounds to find new aldose reductase inhibitors exhibiting superior inhibiting activity and have discovered that a series of new biphenyl derivatives of the formula (I) ##STR2## in which R denotes lower alkyl or cyclohexylmethyl and e,uns/n/ is 2 or 3, have greater activity for inhibiting aldose reductase than those known heretofore.